A fuel cell vehicle includes a fuel cell stack formed by stacking a plurality of fuel cells serving as a power source, a fuel supply system for supplying a hydrogen fuel to the fuel cell stack, an air supply system for supplying oxygen as an oxidant necessary for an electrochemical reaction, a water/heat management system for controlling the temperature of the fuel cell stack, etc.
The fuel supply system is configured such that the compressed hydrogen inside a hydrogen tank is decompressed and then supplied to a fuel electrode (an anode) of the stack. The air supply system is configured such that external air sucked by an air blower is supplied to an air electrode (a cathode) of the stack.
When hydrogen and oxygen are respectively supplied to the fuel electrode and the air electrode of the stack, hydrogen ions are separated through a catalytic reaction at the fuel electrode. The separated hydrogen ions are transferred to an oxidation electrode which is the air electrode via the electrolyte membrane, and the hydrogen ions separated at the fuel electrode may cause an electrochemical reaction together with electrons and oxygen at the oxidation electrode, thereby obtaining electric energy. Specifically, electrochemical oxidation of hydrogen occurs at the fuel electrode, and electrochemical reduction of oxygen takes place at the air electrode. In this case, when the produced electrons move, electric power and heat are created, and water vapor or water is produced by a chemical action for combining the hydrogen with the oxygen.
A discharge device is provided to discharge hydrogen and oxygen which do not react with impurities such as water vapor, water, and heat generated during the production of electric energy of the fuel cell stack, and gases such as water vapor, hydrogen, and oxygen are discharged to the atmosphere via the exhaust path.
The constructions for operating the fuel cells, including an air blower, a hydrogen recirculation blower, a water pump, etc., are connected to a main bus terminal to facilitate starting of the fuel cells. The main bus terminal may be connected with a variety of relays which make it easy to turn power on and off, and a diode for preventing a reverse current from flowing to the fuel cells.
Dry air supplied using the air blower is humidified by a humidifier and supplied to the cathode (the air electrode) of the fuel cell stack. Exhaust gas of the cathode is transferred in a state of being humidified by water generated internally to the humidifier, and thus may be used to humidify the dry air to be supplied to the cathode by the air blower.
Cold starting of a fuel cell vehicle freezes and accumulates ice and frost, and dehydrates the anode. Upon cold starting, a water backflow rate may decrease, and humidification is limitedly generated due to very low saturated water vapor pressure.